1. Field of Invention
The present invention relates generally to folding board systems for producing longitudinal folds in web material and particularly to "W-" folding board systems of a novel form capable of automatically folding web material lengthwise along three parallel fold lines into four equal sections, the resulting folded sections being virtually free of undesirable wrinkles and creases along the section edges and within the interior surface.
2. Description of Background Art
In prior "W-" type folding board systems, various folding board configurations have been used to impart three (3) parallel longitudinal folds in web material such as tissue paper to produce "W-" and inverse "W-" folds, the inverse "W-" fold being the mirror image of the "W-" fold. The "W-" and inverse "W-" folds are formed using left- and right-hand folding board systems respectively, the structure of the left- and right-hand board systems being identical except for the components of the respective systems being disposed in mirror relationship. In use, a series of right-hand systems are positioned in front of left-hand systems, forming a tandem network of folding boards which enables interleaving "W-" with inverse "W-" folded webs. Also a plurality of tiers of tandem networks are formed so that longitudinal multifolding of a plurality of rolls of web material can be effected. When a suitable amount of multifolded interleaved webs are accumulated, the folded webs are cut to a chosen length and inserted into cardboard dispensing cartons as stacks of multifolded interleaved wipers without having connecting perforation tabs therebetween to form packages of dispensable wipers. Dispensing cartons usually have dispensing ports exposed so that efficient "pop-up" sequential dispensing of wipers from the carton can be effected.
Many of the prior techniques for making longitudinal folds have been quite suitable for forming substantial parallel folded sections in multifolded webs but wrinkled sections of folded webs have persisted.
An illustrative environment where application of the principles for the present invention is particularly advantageous is in a system employing two successively positioned folding boards for folding the webs; mainly, a secondary folding board and a primary folding board. Both right- and left-hand folding boards of each kind are used in this system. Left-hand secondary boards are used with left-hand primary folding boards, while right-hand secondary boards are used with right-hand primary folding boards. The left-hand system produces the mirror image of the right-hand system. To prevent describing substantially duplicate structure, only the right-hand system will be described extensively.
In an initial off-the-roll web, the width of each web, illustratively 17 inches, can be considered subdivided into four 41/4 inch width sections; namely, first, second, third and fourth sections respectively, when viewing the web in a horizontal plane from a left edge or "0" edge to a right edge with the first, second and third fold lines disposed in between.
The secondary board is a conventional starter board of the type described in U.S. Pat. No. 3,817,514 to Nisson et al. dated June 8, 1974, but for "W-" folds, it is used to initiate a fold along the first fold line by changing the plane of travel of the first section from a first horizontal plane to a counterclockwise angle of twist of approximately 90 degrees to a first vertical plane.
The primary folding board is a conventional "Z-" folding board of the type which may be configured from the one described in U.S. Pat. No. 3,401,928 to R. H. Frick dated Sept. 17, 1968. This folding board, illustratively provides structure capable of folding the fourth section under the third section while folding the first and second section over the third section as the web travels in the machine direction. During travel over the primary folding board, a guide rod is provided to guide the double panels; e.g., the first and second sections into an overlaying relation with the third section.
In past folding-board systems wherein the web traveling in the machine direction passes over the top surface of the secondary board and substantially under and around the primary board, the surface contour of the web in both the cross and machine directions experiences undesirable stretching, twisting, and drawing together altering the width of the web during travel. These undesirable web alterations occur due to frictional and drag forces imparted to the web by the applied force pulling the web and the structural elements of the boards which the surface of the web contacts as the web interacts with the boards. Ideally, the width of the web should span both boards illustratively the full 17 inches at all times, even during under- and over-folding of the sections. However, probably due to the utilization of empirical techniques to locate active edges and curves of the secondary and primary boards, past designers of the "W-" type folding board apparently failed to consider many of the structural features which would promote maintaining the full span of the web during all web transitions. Many structural considerations have been incorporated in past boards which do oppose extraordinary stretching, twisting, and repressing the web surface; however, wrinkles and creases in the first and second sections of the webs persist. For nearly a decade wrinkles in the surface of the first sections of "W-" folded webs were common. When a stack of longitudinally-folded web material is compressed during cutting, the wrinkled sections throughout the stack are enhanced. Further, when the cut stacks of wipers are stored in cartons, the wrinkled sections become blocked.
As apparent from the foregoing description of the prior-folding systems, rather extensive modifications to the folding systems for controlling primarily the span of the web in a cross-machine direction are needed to form an improved "W-" type folding board system suitable for producing substantially wrinkle-free sections of the web being longitudinally folded. This search was successful and resulted in the present invention.
The present invention is directed to the improved system which resulted from confronting and solving the basic wrinkling problem for the first and second sections of the web as described above. In the course of the development, additional unforeseen problems were also solved as will be apparent.